The method of the invention gives a geopolymer binder used for the ultra rapid treatment of materials, soils or mining discharge containing toxic waste materials. Said geopolymer binder has a setting time equal to or longer than 30 minutes at a temperature of 30 °C and a hardening speed allowing compression resistances (Ac) equal or higher than 15 MPa to be obtained after only 4 hours at 20 °C, when they are tested according the standard applied to mortars of hydraulic binders with a binder/sand ratio equal to 0,38 and a water/binder ratio between 0,22 and 0,27. The preparation method includes the three following reagents: a) an alumino-silicate oxyde (Si2O5, AL2O2) having the Al cation in (IV-V) coordination; b) an alcaline disilicate of sodium and/or potassium, (Na2,K2)(H3SiO4)2; c) a calcium silicate. The molar ratios between the three reagents are equal or between (Na2,K2)(H3SiO4)2/(Si2O5,Al2O2) = 0,40 and 0,60, Ca++/(Si2O5,Al2O2) = 0,60 and 0,40, so that (Na2,K2)(H3SiO4)2 + Ca++/(Si2O5,Al2O2) = 1,0, with Ca++ designating the calcium ion belonging to a weakly basic calcium silicate whose atomic ratio Ca/Si is smaller than 1.